A circulation tool allows a driller to pump out of hole when tripping a drill pipe without the need to make-up a top drive to the drill pipe. A first type of circulation tool is a double-acting cylinder including a main body assembly with drill pipe connections on the top and bottom thereof. Inside the main body assembly, the first circulation tool includes a stinger shaft having an axial bore formed therethrough, a packer cup coupled to a lower end of the stinger shaft, and an internal valve assembly. A pneumatic accumulator is positioned on the outside of the main body assembly.
When the driller turns on a mud pump, mud flows through the first circulation tool. The mud causes the cylinder to extend and the valve to open. While the cylinder extends, air in the annulus of the cylinder is compressed. The valve remains open as the mud continues to flow. When the mud stops flowing, the valve closes, but the cylinder remains extended until the standpipe manifold is bled off to allow the mud on the top side of the tool to drain back into the pit at the surface. When the mud drains, the shaft retracts, due to the pneumatic pressure on the bottom side of the valve.
The operation of the first circulation tool may be dependent upon the operator setting up the first circulation tool with a specific pre-charge or pneumatic pressure on the underside of the tool. If the pressure is too high, the valve in the first circulation tool may not stay open under low-pressure mud flow. If the pressure is too low, the shaft may not retract.
As the first circulation tool relies upon the dynamic flow of mud to keep the valve open and the packer cup sealed, it is difficult to know the flow rate and pressure parameters that the driller must maintain to keep the first circulation tool positively engaged into the drill pipe. A combination of a pneumatic pressure that is too high and a flow rate that is too low may result in “pump out,” causing a mud spill. In addition, the first circulation tool may have a length that requires the driller to run with longer bails to maintain a functional space between the elevator and the first circulation tool, which may require a change of the bails. This results in an increase in rig-up and rig-down time.
A second type of circulation tool may allow the driller to take flow-back when running in-hole. The second circulation tool is pneumatically driven to extend and retract using a control panel at the rig floor with an umbilical connecting the control panel to the second circulation tool. The control panel may provide air to extend and retract the second circulation tool. To extend the second circulation tool, the driller closes the inside blow-out preventer (IBOP), and air is pumped into the upper housing, causing the cylinder to extend and the valve to open. Once extended, the air supply is turned off, and the IBOP is opened, allowing flow-back from the drill pipe to the pit at the surface.
As the second circulation tool is extended, a port on the bottom side of the cylinder is vented to prevent any pressure build-up in the lower housing. Once the second circulation tool is extended and the valve is open, the second circulation tool stays engaged while flow-back pressures are low enough not to cause pump-out. If the driller runs in-hole too fast, however, the flow rate increases, and the pressure drop across the valve may cause the second circulation tool to pump out because there is no positive engagement when the second circulation tool is engaged and accepting flow-back. As with the first circulation tool, the length of the second circulation tool may also require the change of bails.
In addition, the first and second circulation tools may both render the top drive pipe-handler redundant and/or inaccessible for make-up of the top drive to the drill pipe because the first and second circulation tools may be positioned below the saver sub. This may compromise and change the operation when the top drive needs to be screwed into the drill pipe.